[PATCH v2 0/4] Support spread spectrum clocking for stm32f{4,7} platforms

[PATCH v2 0/4] Support spread spectrum clocking for stm32f{4,7} platforms

[Dario Binacchi]

The series adds support for spread spectrum clocking for stm32f{4,7}
main PLL.

To achieve this, it was considered necessary to also apply patches to
improve the documentation (conversion of `st,stm32-rcc.txt` according to
the json-schema) and the code (use of FIELD helpers).

The series has been tested on the STM32F469I-DISCO board.

Changes in v2:
- Fixup patches:
  2/6 dt-bindings: reset: st,stm32-rcc: update reference due to rename
  3/6 dt-bindings: clock: stm32fx: update reference due to rename
  to
  1/6 dt-bindings: clock: convert stm32 rcc bindings to json-schema
- Changes to dt-bindings: clock: convert stm32 rcc bindings to json-schema
- Changes to dt-bindings: clock: st,stm32-rcc: support spread spectrum clocking

Dario Binacchi (4):
  dt-bindings: clock: convert stm32 rcc bindings to json-schema
  dt-bindings: clock: st,stm32-rcc: support spread spectrum clocking
  clk: stm32f4: use FIELD helpers to access the PLLCFGR fields
  clk: stm32f4: support spread spectrum clock generation

 .../bindings/clock/st,stm32-rcc.txt           | 138 ----------------
 .../bindings/clock/st,stm32-rcc.yaml          | 147 +++++++++++++++++
 .../bindings/reset/st,stm32-rcc.txt           |   2 +-
 drivers/clk/clk-stm32f4.c                     | 155 +++++++++++++++++-
 include/dt-bindings/clock/stm32fx-clock.h     |   2 +-
 5 files changed, 298 insertions(+), 146 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/clock/st,stm32-rcc.txt
 create mode 100644 Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml

-- 
2.43.0

[PATCH v2 1/4] dt-bindings: clock: convert stm32 rcc bindings to json-schema

[Dario Binacchi]

The patch converts st,stm32-rcc.txt to the JSON schema, but it does more
than that. The old bindings, in fact, only covered the stm32f{4,7}
platforms and not the stm32h7. Therefore, to avoid patch submission tests
failing, it was necessary to add the corresponding compatible (i. e.
st,stm32h743-rcc) and specify that, in this case, 3 are the clocks instead
of the 2 required for the stm32f{4,7} platforms.
Additionally, the old bindings made no mention of the st,syscfg property,
which is used by both the stm32f{4,7} and the stm32h7 platforms.

The patch also fixes the files referencing to the old st,stm32-rcc.txt.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
---

Changes in v2:
- Fixup patches:
  2/6 dt-bindings: reset: st,stm32-rcc: update reference due to rename
  3/6 dt-bindings: clock: stm32fx: update reference due to rename
- Update the commit message
- Reduce the description section of the yaml file
- List the items with description for the clocks property
- Use only one example
- Rename rcc to clock-controller@58024400 for the node of the example

 .../bindings/clock/st,stm32-rcc.txt           | 138 ------------------
 .../bindings/clock/st,stm32-rcc.yaml          | 111 ++++++++++++++
 .../bindings/reset/st,stm32-rcc.txt           |   2 +-
 include/dt-bindings/clock/stm32fx-clock.h     |   2 +-
 4 files changed, 113 insertions(+), 140 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/clock/st,stm32-rcc.txt
 create mode 100644 Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml

diff --git a/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt b/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt
deleted file mode 100644
index cfa04b614d8a..000000000000
--- a/Documentation/devicetree/bindings/clock/st,stm32-rcc.txt
+++ /dev/null
@@ -1,138 +0,0 @@
-STMicroelectronics STM32 Reset and Clock Controller
-===================================================
-
-The RCC IP is both a reset and a clock controller.
-
-Please refer to clock-bindings.txt for common clock controller binding usage.
-Please also refer to reset.txt for common reset controller binding usage.
-
-Required properties:
-- compatible: Should be:
-  "st,stm32f42xx-rcc"
-  "st,stm32f469-rcc"
-  "st,stm32f746-rcc"
-  "st,stm32f769-rcc"
-
-- reg: should be register base and length as documented in the
-  datasheet
-- #reset-cells: 1, see below
-- #clock-cells: 2, device nodes should specify the clock in their "clocks"
-  property, containing a phandle to the clock device node, an index selecting
-  between gated clocks and other clocks and an index specifying the clock to
-  use.
-- clocks: External oscillator clock phandle
-  - high speed external clock signal (HSE)
-  - external I2S clock (I2S_CKIN)
-
-Example:
-
-	rcc: rcc@40023800 {
-		#reset-cells = <1>;
-		#clock-cells = <2>
-		compatible = "st,stm32f42xx-rcc", "st,stm32-rcc";
-		reg = <0x40023800 0x400>;
-		clocks = <&clk_hse>, <&clk_i2s_ckin>;
-	};
-
-Specifying gated clocks
-=======================
-
-The primary index must be set to 0.
-
-The secondary index is the bit number within the RCC register bank, starting
-from the first RCC clock enable register (RCC_AHB1ENR, address offset 0x30).
-
-It is calculated as: index = register_offset / 4 * 32 + bit_offset.
-Where bit_offset is the bit offset within the register (LSB is 0, MSB is 31).
-
-To simplify the usage and to share bit definition with the reset and clock
-drivers of the RCC IP, macros are available to generate the index in
-human-readble format.
-
-For STM32F4 series, the macro are available here:
- - include/dt-bindings/mfd/stm32f4-rcc.h
-
-Example:
-
-	/* Gated clock, AHB1 bit 0 (GPIOA) */
-	... {
-		clocks = <&rcc 0 STM32F4_AHB1_CLOCK(GPIOA)>
-	};
-
-	/* Gated clock, AHB2 bit 4 (CRYP) */
-	... {
-		clocks = <&rcc 0 STM32F4_AHB2_CLOCK(CRYP)>
-	};
-
-Specifying other clocks
-=======================
-
-The primary index must be set to 1.
-
-The secondary index is bound with the following magic numbers:
-
-	0	SYSTICK
-	1	FCLK
-	2	CLK_LSI		(low-power clock source)
-	3	CLK_LSE		(generated from a 32.768 kHz low-speed external
-				 crystal or ceramic resonator)
-	4	CLK_HSE_RTC	(HSE division factor for RTC clock)
-	5	CLK_RTC		(real-time clock)
-	6	PLL_VCO_I2S	(vco frequency of I2S pll)
-	7	PLL_VCO_SAI	(vco frequency of SAI pll)
-	8	CLK_LCD		(LCD-TFT)
-	9	CLK_I2S		(I2S clocks)
-	10	CLK_SAI1	(audio clocks)
-	11	CLK_SAI2
-	12	CLK_I2SQ_PDIV	(post divisor of pll i2s q divisor)
-	13	CLK_SAIQ_PDIV	(post divisor of pll sai q divisor)
-
-	14	CLK_HSI		(Internal ocscillator clock)
-	15	CLK_SYSCLK	(System Clock)
-	16	CLK_HDMI_CEC	(HDMI-CEC clock)
-	17	CLK_SPDIF	(SPDIF-Rx clock)
-	18	CLK_USART1	(U(s)arts clocks)
-	19	CLK_USART2
-	20	CLK_USART3
-	21	CLK_UART4
-	22	CLK_UART5
-	23	CLK_USART6
-	24	CLK_UART7
-	25	CLK_UART8
-	26	CLK_I2C1	(I2S clocks)
-	27	CLK_I2C2
-	28	CLK_I2C3
-	29	CLK_I2C4
-	30	CLK_LPTIMER	(LPTimer1 clock)
-	31	CLK_PLL_SRC
-	32	CLK_DFSDM1
-	33	CLK_ADFSDM1
-	34	CLK_F769_DSI
-)
-
-Example:
-
-	/* Misc clock, FCLK */
-	... {
-		clocks = <&rcc 1 STM32F4_APB1_CLOCK(TIM2)>
-	};
-
-
-Specifying softreset control of devices
-=======================================
-
-Device nodes should specify the reset channel required in their "resets"
-property, containing a phandle to the reset device node and an index specifying
-which channel to use.
-The index is the bit number within the RCC registers bank, starting from RCC
-base address.
-It is calculated as: index = register_offset / 4 * 32 + bit_offset.
-Where bit_offset is the bit offset within the register.
-For example, for CRC reset:
-  crc = AHB1RSTR_offset / 4 * 32 + CRCRST_bit_offset = 0x10 / 4 * 32 + 12 = 140
-
-example:
-
-	timer2 {
-		resets	= <&rcc STM32F4_APB1_RESET(TIM2)>;
-	};
diff --git a/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml b/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml
new file mode 100644
index 000000000000..779e547700be
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml
@@ -0,0 +1,111 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/st,stm32-rcc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: STMicroelectronics STM32 Reset Clock Controller
+
+maintainers:
+  - Dario Binacchi <dario.binacchi@amarulasolutions.com>
+
+description: |
+  The RCC IP is both a reset and a clock controller.
+  The reset phandle argument is the bit number within the RCC registers bank,
+  starting from RCC base address.
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - const: st,stm32f42xx-rcc
+          - const: st,stm32-rcc
+      - items:
+          - enum:
+              - st,stm32f469-rcc
+          - const: st,stm32f42xx-rcc
+          - const: st,stm32-rcc
+      - items:
+          - const: st,stm32f746-rcc
+          - const: st,stm32-rcc
+      - items:
+          - enum:
+              - st,stm32f769-rcc
+          - const: st,stm32f746-rcc
+          - const: st,stm32-rcc
+      - items:
+          - const: st,stm32h743-rcc
+          - const: st,stm32-rcc
+
+  reg:
+    maxItems: 1
+
+  '#reset-cells':
+    const: 1
+
+  '#clock-cells':
+    enum: [1, 2]
+
+  clocks:
+    minItems: 2
+    maxItems: 3
+
+  st,syscfg:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      Phandle to system configuration controller. It can be used to control the
+      power domain circuitry.
+
+required:
+  - compatible
+  - reg
+  - '#reset-cells'
+  - '#clock-cells'
+  - clocks
+  - st,syscfg
+
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: st,stm32h743-rcc
+    then:
+      properties:
+        '#clock-cells':
+          const: 1
+          description: |
+            The clock index for the specified type.
+        clocks:
+          items:
+            - description: high speed external (HSE) clock input
+            - description: low speed external (LSE) clock input
+            - description: Inter-IC sound (I2S) clock input
+    else:
+      properties:
+        '#clock-cells':
+          const: 2
+          description: |
+            - The first cell is the clock type, possible values are 0 for
+              gated clocks and 1 otherwise.
+            - The second cell is the clock index for the specified type.
+        clocks:
+          items:
+            - description: high speed external (HSE) clock input
+            - description: Inter-IC sound (I2S) clock input
+
+additionalProperties: false
+
+examples:
+  # Reset and Clock Control Module node:
+  - |
+    clock-controller@58024400 {
+        compatible = "st,stm32h743-rcc", "st,stm32-rcc";
+        reg = <0x58024400 0x400>;
+        #clock-cells = <1>;
+        #reset-cells = <1>;
+        clocks = <&clk_hse>, <&clk_lse>, <&clk_i2s>;
+        st,syscfg = <&pwrcfg>;
+    };
+
+...
diff --git a/Documentation/devicetree/bindings/reset/st,stm32-rcc.txt b/Documentation/devicetree/bindings/reset/st,stm32-rcc.txt
index 01db34375192..384035e8e60b 100644
--- a/Documentation/devicetree/bindings/reset/st,stm32-rcc.txt
+++ b/Documentation/devicetree/bindings/reset/st,stm32-rcc.txt
@@ -3,4 +3,4 @@ STMicroelectronics STM32 Peripheral Reset Controller
 
 The RCC IP is both a reset and a clock controller.
 
-Please see Documentation/devicetree/bindings/clock/st,stm32-rcc.txt
+Please see Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml
diff --git a/include/dt-bindings/clock/stm32fx-clock.h b/include/dt-bindings/clock/stm32fx-clock.h
index e5dad050d518..b6ff9c68cb3f 100644
--- a/include/dt-bindings/clock/stm32fx-clock.h
+++ b/include/dt-bindings/clock/stm32fx-clock.h
@@ -10,7 +10,7 @@
  * List of clocks which are not derived from system clock (SYSCLOCK)
  *
  * The index of these clocks is the secondary index of DT bindings
- * (see Documentation/devicetree/bindings/clock/st,stm32-rcc.txt)
+ * (see Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml)
  *
  * e.g:
 	<assigned-clocks = <&rcc 1 CLK_LSE>;
-- 
2.43.0

Re: [PATCH v2 1/4] dt-bindings: clock: convert stm32 rcc bindings to json-schema

[Krzysztof Kozlowski]

On Thu, Jan 09, 2025 at 10:18:28PM +0100, Dario Binacchi wrote:
> +maintainers:
> +  - Dario Binacchi <dario.binacchi@amarulasolutions.com>
> +
> +description: |
> +  The RCC IP is both a reset and a clock controller.
> +  The reset phandle argument is the bit number within the RCC registers bank,
> +  starting from RCC base address.
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - items:
> +          - const: st,stm32f42xx-rcc
> +          - const: st,stm32-rcc
> +      - items:
> +          - enum:
> +              - st,stm32f469-rcc
> +          - const: st,stm32f42xx-rcc
> +          - const: st,stm32-rcc
> +      - items:
> +          - const: st,stm32f746-rcc

Why this isn't just part of enum with first group/list? Different
groups/lists are for different fallbacks and I am pretty sure fallback
is the same.

> +          - const: st,stm32-rcc
> +      - items:
> +          - enum:
> +              - st,stm32f769-rcc
> +          - const: st,stm32f746-rcc
> +          - const: st,stm32-rcc
> +      - items:
> +          - const: st,stm32h743-rcc

Same here.

Rest looks good, so with combining entries above:

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof

Re: [PATCH v2 1/4] dt-bindings: clock: convert stm32 rcc bindings to json-schema

[Dario Binacchi]

On Sat, Jan 11, 2025 at 10:25 AM Krzysztof Kozlowski <krzk@kernel.org> wrote:
>
> On Thu, Jan 09, 2025 at 10:18:28PM +0100, Dario Binacchi wrote:
> > +maintainers:
> > +  - Dario Binacchi <dario.binacchi@amarulasolutions.com>
> > +
> > +description: |
> > +  The RCC IP is both a reset and a clock controller.
> > +  The reset phandle argument is the bit number within the RCC registers bank,
> > +  starting from RCC base address.
> > +
> > +properties:
> > +  compatible:
> > +    oneOf:
> > +      - items:
> > +          - const: st,stm32f42xx-rcc
> > +          - const: st,stm32-rcc
> > +      - items:
> > +          - enum:
> > +              - st,stm32f469-rcc
> > +          - const: st,stm32f42xx-rcc
> > +          - const: st,stm32-rcc
> > +      - items:
> > +          - const: st,stm32f746-rcc
>
> Why this isn't just part of enum with first group/list? Different
> groups/lists are for different fallbacks and I am pretty sure fallback
> is the same.

I tried running tests after applying the changes you suggested, but
the tests are failing.
Thanks and regards,
Dario

>
> > +          - const: st,stm32-rcc
> > +      - items:
> > +          - enum:
> > +              - st,stm32f769-rcc
> > +          - const: st,stm32f746-rcc
> > +          - const: st,stm32-rcc
> > +      - items:
> > +          - const: st,stm32h743-rcc
>
> Same here.
>
> Rest looks good, so with combining entries above:
>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>
> Best regards,
> Krzysztof
>


-- 

Dario Binacchi

Senior Embedded Linux Developer

dario.binacchi@amarulasolutions.com

__________________________________


Amarula Solutions SRL

Via Le Canevare 30, 31100 Treviso, Veneto, IT

T. +39 042 243 5310
info@amarulasolutions.com

www.amarulasolutions.com

Re: [PATCH v2 1/4] dt-bindings: clock: convert stm32 rcc bindings to json-schema

[Krzysztof Kozlowski]

On 14/01/2025 10:10, Dario Binacchi wrote:
> On Sat, Jan 11, 2025 at 10:25 AM Krzysztof Kozlowski <krzk@kernel.org> wrote:
>>
>> On Thu, Jan 09, 2025 at 10:18:28PM +0100, Dario Binacchi wrote:
>>> +maintainers:
>>> +  - Dario Binacchi <dario.binacchi@amarulasolutions.com>
>>> +
>>> +description: |
>>> +  The RCC IP is both a reset and a clock controller.
>>> +  The reset phandle argument is the bit number within the RCC registers bank,
>>> +  starting from RCC base address.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    oneOf:
>>> +      - items:
>>> +          - const: st,stm32f42xx-rcc
>>> +          - const: st,stm32-rcc
>>> +      - items:
>>> +          - enum:
>>> +              - st,stm32f469-rcc
>>> +          - const: st,stm32f42xx-rcc
>>> +          - const: st,stm32-rcc
>>> +      - items:
>>> +          - const: st,stm32f746-rcc
>>
>> Why this isn't just part of enum with first group/list? Different
>> groups/lists are for different fallbacks and I am pretty sure fallback
>> is the same.
> 
> I tried running tests after applying the changes you suggested, but
> the tests are failing.
And? Fix the code then?

Best regards,
Krzysztof

[PATCH v2 2/4] dt-bindings: clock: st,stm32-rcc: support spread spectrum clocking

[Dario Binacchi]

The addition of DT bindings for enabling and tuning spread spectrum
clocking generation is available only for the main PLL of stm32f{4,7}
platforms.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

---

Changes in v2:
- Update the commit message
- Change st,ssc-modmethod type from non-unique-string-array to string

 .../bindings/clock/st,stm32-rcc.yaml          | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml b/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml
index 779e547700be..628bbbcf2875 100644
--- a/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml
+++ b/Documentation/devicetree/bindings/clock/st,stm32-rcc.yaml
@@ -56,6 +56,26 @@ properties:
       Phandle to system configuration controller. It can be used to control the
       power domain circuitry.
 
+  st,ssc-modfreq-hz:
+    description:
+      The modulation frequency for main PLL (in Hz)
+
+  st,ssc-moddepth-permyriad:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      The modulation rate for main PLL (in permyriad, i.e. 0.01%)
+    minimum: 25
+    maximum: 200
+
+  st,ssc-modmethod:
+    $ref: /schemas/types.yaml#/definitions/string
+    description:
+      The modulation techniques for main PLL.
+    items:
+      enum:
+        - center-spread
+        - down-spread
+
 required:
   - compatible
   - reg
@@ -81,6 +101,10 @@ allOf:
             - description: high speed external (HSE) clock input
             - description: low speed external (LSE) clock input
             - description: Inter-IC sound (I2S) clock input
+        st,ssc-modfreq-hz: false
+        st,ssc-moddepth-permyriad: false
+        st,ssc-modmethod: false
+
     else:
       properties:
         '#clock-cells':
@@ -98,6 +122,18 @@ additionalProperties: false
 
 examples:
   # Reset and Clock Control Module node:
+  - |
+    clock-controller@40023800 {
+        compatible = "st,stm32f42xx-rcc", "st,stm32-rcc";
+        reg = <0x40023800 0x400>;
+        #clock-cells = <2>;
+        #reset-cells = <1>;
+        clocks = <&clk_hse>, <&clk_i2s_ckin>;
+        st,syscfg = <&pwrcfg>;
+        st,ssc-modfreq-hz = <10000>;
+        st,ssc-moddepth-permyriad = <200>;
+        st,ssc-modmethod = "center-spread";
+    };
   - |
     clock-controller@58024400 {
         compatible = "st,stm32h743-rcc", "st,stm32-rcc";
-- 
2.43.0

Re: [PATCH v2 2/4] dt-bindings: clock: st,stm32-rcc: support spread spectrum clocking

[Krzysztof Kozlowski]

On Thu, Jan 09, 2025 at 10:18:29PM +0100, Dario Binacchi wrote:
> The addition of DT bindings for enabling and tuning spread spectrum
> clocking generation is available only for the main PLL of stm32f{4,7}
> platforms.
> 
> Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
> 
> ---

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof

[PATCH v2 3/4] clk: stm32f4: use FIELD helpers to access the PLLCFGR fields

[Dario Binacchi]

Use GENMASK() along with FIELD_GET() and FIELD_PREP() helpers to access
the PLLCFGR fields instead of manually masking and shifting.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
---

(no changes since v1)

 drivers/clk/clk-stm32f4.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/clk-stm32f4.c b/drivers/clk/clk-stm32f4.c
index 07c13ebe327d..db1c56c8d54f 100644
--- a/drivers/clk/clk-stm32f4.c
+++ b/drivers/clk/clk-stm32f4.c
@@ -5,6 +5,7 @@
  * Inspired by clk-asm9260.c .
  */
 
+#include <linux/bitfield.h>
 #include <linux/clk-provider.h>
 #include <linux/err.h>
 #include <linux/io.h>
@@ -39,6 +40,8 @@
 #define STM32F4_RCC_DCKCFGR		0x8c
 #define STM32F7_RCC_DCKCFGR2		0x90
 
+#define STM32F4_RCC_PLLCFGR_N_MASK	GENMASK(14, 6)
+
 #define NONE -1
 #define NO_IDX  NONE
 #define NO_MUX  NONE
@@ -632,9 +635,11 @@ static unsigned long stm32f4_pll_recalc(struct clk_hw *hw,
 {
 	struct clk_gate *gate = to_clk_gate(hw);
 	struct stm32f4_pll *pll = to_stm32f4_pll(gate);
+	unsigned long val;
 	unsigned long n;
 
-	n = (readl(base + pll->offset) >> 6) & 0x1ff;
+	val = readl(base + pll->offset);
+	n = FIELD_GET(STM32F4_RCC_PLLCFGR_N_MASK, val);
 
 	return parent_rate * n;
 }
@@ -673,9 +678,10 @@ static int stm32f4_pll_set_rate(struct clk_hw *hw, unsigned long rate,
 
 	n = rate  / parent_rate;
 
-	val = readl(base + pll->offset) & ~(0x1ff << 6);
+	val = readl(base + pll->offset) & ~STM32F4_RCC_PLLCFGR_N_MASK;
+	val |= FIELD_PREP(STM32F4_RCC_PLLCFGR_N_MASK, n);
 
-	writel(val | ((n & 0x1ff) <<  6), base + pll->offset);
+	writel(val, base + pll->offset);
 
 	if (pll_state)
 		stm32f4_pll_enable(hw);
-- 
2.43.0

[PATCH v2 4/4] clk: stm32f4: support spread spectrum clock generation

[Dario Binacchi]

Support spread spectrum clock generation for the main PLL, the only one
for which this functionality is available.

Tested on the STM32F469I-DISCO board.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

---

Changes in v2:
- Fixup patches:
  2/6 dt-bindings: reset: st,stm32-rcc: update reference due to rename
  3/6 dt-bindings: clock: stm32fx: update reference due to rename
  to
  1/6 dt-bindings: clock: convert stm32 rcc bindings to json-schema
- Changes to dt-bindings: clock: convert stm32 rcc bindings to json-schema
- Changes to dt-bindings: clock: st,stm32-rcc: support spread spectrum clocking

 drivers/clk/clk-stm32f4.c | 143 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 140 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/clk-stm32f4.c b/drivers/clk/clk-stm32f4.c
index db1c56c8d54f..6c80c0dbb0a3 100644
--- a/drivers/clk/clk-stm32f4.c
+++ b/drivers/clk/clk-stm32f4.c
@@ -35,6 +35,7 @@
 #define STM32F4_RCC_APB2ENR		0x44
 #define STM32F4_RCC_BDCR		0x70
 #define STM32F4_RCC_CSR			0x74
+#define STM32F4_RCC_SSCGR		0x80
 #define STM32F4_RCC_PLLI2SCFGR		0x84
 #define STM32F4_RCC_PLLSAICFGR		0x88
 #define STM32F4_RCC_DCKCFGR		0x8c
@@ -42,6 +43,12 @@
 
 #define STM32F4_RCC_PLLCFGR_N_MASK	GENMASK(14, 6)
 
+#define STM32F4_RCC_SSCGR_SSCGEN	BIT(31)
+#define STM32F4_RCC_SSCGR_SPREADSEL	BIT(30)
+#define STM32F4_RCC_SSCGR_RESERVED_MASK	GENMASK(29, 28)
+#define STM32F4_RCC_SSCGR_INCSTEP_MASK	GENMASK(27, 13)
+#define STM32F4_RCC_SSCGR_MODPER_MASK	GENMASK(12, 0)
+
 #define NONE -1
 #define NO_IDX  NONE
 #define NO_MUX  NONE
@@ -512,6 +519,17 @@ static const struct clk_div_table pll_divr_table[] = {
 	{ 2, 2 }, { 3, 3 }, { 4, 4 }, { 5, 5 }, { 6, 6 }, { 7, 7 }, { 0 }
 };
 
+enum stm32f4_pll_ssc_mod_type {
+	STM32F4_PLL_SSC_CENTER_SPREAD,
+	STM32F4_PLL_SSC_DOWN_SPREAD,
+};
+
+struct stm32f4_pll_ssc {
+	unsigned int mod_freq;
+	unsigned int mod_depth;
+	enum stm32f4_pll_ssc_mod_type mod_type;
+};
+
 struct stm32f4_pll {
 	spinlock_t *lock;
 	struct	clk_gate gate;
@@ -519,6 +537,8 @@ struct stm32f4_pll {
 	u8 bit_rdy_idx;
 	u8 status;
 	u8 n_start;
+	bool ssc_enable;
+	struct stm32f4_pll_ssc ssc_conf;
 };
 
 #define to_stm32f4_pll(_gate) container_of(_gate, struct stm32f4_pll, gate)
@@ -541,6 +561,7 @@ struct stm32f4_vco_data {
 	u8 offset;
 	u8 bit_idx;
 	u8 bit_rdy_idx;
+	bool sscg;
 };
 
 static const struct stm32f4_vco_data  vco_data[] = {
@@ -661,6 +682,34 @@ static long stm32f4_pll_round_rate(struct clk_hw *hw, unsigned long rate,
 	return *prate * n;
 }
 
+static void stm32f4_pll_set_ssc(struct clk_hw *hw, unsigned long parent_rate,
+				unsigned int ndiv)
+{
+	struct clk_gate *gate = to_clk_gate(hw);
+	struct stm32f4_pll *pll = to_stm32f4_pll(gate);
+	struct stm32f4_pll_ssc *ssc = &pll->ssc_conf;
+	u32 modeper, incstep;
+	u32 sscgr;
+
+	sscgr = readl(base + STM32F4_RCC_SSCGR);
+	/* reserved field must be kept at reset value */
+	sscgr &= STM32F4_RCC_SSCGR_RESERVED_MASK;
+
+	modeper = DIV_ROUND_CLOSEST(parent_rate, 4 * ssc->mod_freq);
+	incstep = DIV_ROUND_CLOSEST(((1 << 15) - 1) * ssc->mod_depth * ndiv,
+				    5 * 10000 * modeper);
+	sscgr |= STM32F4_RCC_SSCGR_SSCGEN |
+		FIELD_PREP(STM32F4_RCC_SSCGR_INCSTEP_MASK, incstep) |
+		FIELD_PREP(STM32F4_RCC_SSCGR_MODPER_MASK, modeper);
+
+	if (ssc->mod_type)
+		sscgr |= STM32F4_RCC_SSCGR_SPREADSEL;
+
+	pr_debug("%s: pll: %s: modeper: %d, incstep: %d, sscgr: 0x%08x\n",
+		 __func__, clk_hw_get_name(hw), modeper, incstep, sscgr);
+	writel(sscgr, base + STM32F4_RCC_SSCGR);
+}
+
 static int stm32f4_pll_set_rate(struct clk_hw *hw, unsigned long rate,
 				unsigned long parent_rate)
 {
@@ -683,6 +732,9 @@ static int stm32f4_pll_set_rate(struct clk_hw *hw, unsigned long rate,
 
 	writel(val, base + pll->offset);
 
+	if (pll->ssc_enable)
+		stm32f4_pll_set_ssc(hw, parent_rate, n);
+
 	if (pll_state)
 		stm32f4_pll_enable(hw);
 
@@ -788,6 +840,87 @@ static struct clk_hw *clk_register_pll_div(const char *name,
 	return hw;
 }
 
+static int stm32f4_pll_init_ssc(struct clk_hw *hw, struct stm32f4_pll_ssc *conf)
+{
+	struct clk_gate *gate = to_clk_gate(hw);
+	struct stm32f4_pll *pll = to_stm32f4_pll(gate);
+	struct clk_hw *parent;
+	unsigned long parent_rate;
+	int pll_state;
+	unsigned long n, val;
+
+	parent = clk_hw_get_parent(hw);
+	if (!parent) {
+		pr_err("%s: failed to get clock parent\n", __func__);
+		return -ENODEV;
+	}
+
+	parent_rate = clk_hw_get_rate(parent);
+
+	pll->ssc_enable = true;
+	memcpy(&pll->ssc_conf, conf, sizeof(pll->ssc_conf));
+
+	pll_state = stm32f4_pll_is_enabled(hw);
+
+	if (pll_state)
+		stm32f4_pll_disable(hw);
+
+	val = readl(base + pll->offset);
+	n = FIELD_GET(STM32F4_RCC_PLLCFGR_N_MASK, val);
+
+	pr_debug("%s: pll: %s, parent: %s, parent-rate: %lu, n: %lu\n",
+		 __func__, clk_hw_get_name(hw), clk_hw_get_name(parent),
+		 parent_rate, n);
+
+	stm32f4_pll_set_ssc(hw, parent_rate, n);
+
+	if (pll_state)
+		stm32f4_pll_enable(hw);
+
+	return 0;
+}
+
+static int stm32f4_pll_ssc_parse_dt(struct device_node *np,
+				    struct stm32f4_pll_ssc *conf)
+{
+	int ret;
+	const char *s;
+
+	if (!conf)
+		return -EINVAL;
+
+	ret = of_property_read_u32(np, "st,ssc-modfreq-hz", &conf->mod_freq);
+	if (ret)
+		return ret;
+
+	ret = of_property_read_u32(np, "st,ssc-moddepth-permyriad",
+				   &conf->mod_depth);
+	if (ret) {
+		pr_err("%pOF: missing st,ssc-moddepth-permyriad\n", np);
+		return ret;
+	}
+
+	ret = of_property_read_string(np, "st,ssc-modmethod", &s);
+	if (ret) {
+		pr_err("%pOF: missing st,ssc-modmethod\n", np);
+		return ret;
+	}
+
+	if (!strcmp(s, "down-spread")) {
+		conf->mod_type = STM32F4_PLL_SSC_DOWN_SPREAD;
+	} else if (!strcmp(s, "center-spread")) {
+		conf->mod_type = STM32F4_PLL_SSC_CENTER_SPREAD;
+	} else {
+		pr_err("%pOF: wrong value (%s) for fsl,ssc-modmethod\n", np, s);
+		return -EINVAL;
+	}
+
+	pr_debug("%pOF: SSCG settings: mod_freq: %d, mod_depth: %d mod_method: %s [%d]\n",
+		 np, conf->mod_freq, conf->mod_depth, s, conf->mod_type);
+
+	return 0;
+}
+
 static struct clk_hw *stm32f4_rcc_register_pll(const char *pllsrc,
 		const struct stm32f4_pll_data *data,  spinlock_t *lock)
 {
@@ -1695,7 +1828,8 @@ static void __init stm32f4_rcc_init(struct device_node *np)
 	const struct of_device_id *match;
 	const struct stm32f4_clk_data *data;
 	unsigned long pllm;
-	struct clk_hw *pll_src_hw;
+	struct clk_hw *pll_src_hw, *pll_vco_hw;
+	struct stm32f4_pll_ssc ssc_conf;
 
 	base = of_iomap(np, 0);
 	if (!base) {
@@ -1754,8 +1888,8 @@ static void __init stm32f4_rcc_init(struct device_node *np)
 	clk_hw_register_fixed_factor(NULL, "vco_in", pll_src,
 				     0, 1, pllm);
 
-	stm32f4_rcc_register_pll("vco_in", &data->pll_data[0],
-			&stm32f4_clk_lock);
+	pll_vco_hw = stm32f4_rcc_register_pll("vco_in", &data->pll_data[0],
+					      &stm32f4_clk_lock);
 
 	clks[PLL_VCO_I2S] = stm32f4_rcc_register_pll("vco_in",
 			&data->pll_data[1], &stm32f4_clk_lock);
@@ -1900,6 +2034,9 @@ static void __init stm32f4_rcc_init(struct device_node *np)
 
 	of_clk_add_hw_provider(np, stm32f4_rcc_lookup_clk, NULL);
 
+	if (!stm32f4_pll_ssc_parse_dt(np, &ssc_conf))
+		stm32f4_pll_init_ssc(pll_vco_hw, &ssc_conf);
+
 	return;
 fail:
 	kfree(clks);
-- 
2.43.0

Re: [PATCH v2 4/4] clk: stm32f4: support spread spectrum clock generation

[Stephen Boyd]

Quoting Dario Binacchi (2025-01-09 13:18:31)
> diff --git a/drivers/clk/clk-stm32f4.c b/drivers/clk/clk-stm32f4.c
> index db1c56c8d54f..6c80c0dbb0a3 100644
> --- a/drivers/clk/clk-stm32f4.c
> +++ b/drivers/clk/clk-stm32f4.c
> @@ -35,6 +35,7 @@
>  #define STM32F4_RCC_APB2ENR            0x44
>  #define STM32F4_RCC_BDCR               0x70
>  #define STM32F4_RCC_CSR                        0x74
> +#define STM32F4_RCC_SSCGR              0x80
>  #define STM32F4_RCC_PLLI2SCFGR         0x84
>  #define STM32F4_RCC_PLLSAICFGR         0x88
>  #define STM32F4_RCC_DCKCFGR            0x8c
> @@ -42,6 +43,12 @@
>  
>  #define STM32F4_RCC_PLLCFGR_N_MASK     GENMASK(14, 6)
>  
> +#define STM32F4_RCC_SSCGR_SSCGEN       BIT(31)
> +#define STM32F4_RCC_SSCGR_SPREADSEL    BIT(30)
> +#define STM32F4_RCC_SSCGR_RESERVED_MASK        GENMASK(29, 28)
> +#define STM32F4_RCC_SSCGR_INCSTEP_MASK GENMASK(27, 13)
> +#define STM32F4_RCC_SSCGR_MODPER_MASK  GENMASK(12, 0)
> +
>  #define NONE -1
>  #define NO_IDX  NONE
>  #define NO_MUX  NONE
> @@ -512,6 +519,17 @@ static const struct clk_div_table pll_divr_table[] = {
>         { 2, 2 }, { 3, 3 }, { 4, 4 }, { 5, 5 }, { 6, 6 }, { 7, 7 }, { 0 }
>  };
>  
> +enum stm32f4_pll_ssc_mod_type {
> +       STM32F4_PLL_SSC_CENTER_SPREAD,
> +       STM32F4_PLL_SSC_DOWN_SPREAD,
> +};
> +
> +struct stm32f4_pll_ssc {
> +       unsigned int mod_freq;
> +       unsigned int mod_depth;
> +       enum stm32f4_pll_ssc_mod_type mod_type;
> +};
> +
>  struct stm32f4_pll {
>         spinlock_t *lock;
>         struct  clk_gate gate;
> @@ -519,6 +537,8 @@ struct stm32f4_pll {
>         u8 bit_rdy_idx;
>         u8 status;
>         u8 n_start;
> +       bool ssc_enable;
> +       struct stm32f4_pll_ssc ssc_conf;
>  };
>  
>  #define to_stm32f4_pll(_gate) container_of(_gate, struct stm32f4_pll, gate)
> @@ -541,6 +561,7 @@ struct stm32f4_vco_data {
>         u8 offset;
>         u8 bit_idx;
>         u8 bit_rdy_idx;
> +       bool sscg;
>  };
>  
>  static const struct stm32f4_vco_data  vco_data[] = {
> @@ -661,6 +682,34 @@ static long stm32f4_pll_round_rate(struct clk_hw *hw, unsigned long rate,
>         return *prate * n;
>  }
>  
> +static void stm32f4_pll_set_ssc(struct clk_hw *hw, unsigned long parent_rate,
> +                               unsigned int ndiv)
> +{
> +       struct clk_gate *gate = to_clk_gate(hw);
> +       struct stm32f4_pll *pll = to_stm32f4_pll(gate);
> +       struct stm32f4_pll_ssc *ssc = &pll->ssc_conf;
> +       u32 modeper, incstep;
> +       u32 sscgr;
> +
> +       sscgr = readl(base + STM32F4_RCC_SSCGR);
> +       /* reserved field must be kept at reset value */
> +       sscgr &= STM32F4_RCC_SSCGR_RESERVED_MASK;
> +
> +       modeper = DIV_ROUND_CLOSEST(parent_rate, 4 * ssc->mod_freq);
> +       incstep = DIV_ROUND_CLOSEST(((1 << 15) - 1) * ssc->mod_depth * ndiv,
> +                                   5 * 10000 * modeper);
> +       sscgr |= STM32F4_RCC_SSCGR_SSCGEN |
> +               FIELD_PREP(STM32F4_RCC_SSCGR_INCSTEP_MASK, incstep) |
> +               FIELD_PREP(STM32F4_RCC_SSCGR_MODPER_MASK, modeper);
> +
> +       if (ssc->mod_type)
> +               sscgr |= STM32F4_RCC_SSCGR_SPREADSEL;
> +
> +       pr_debug("%s: pll: %s: modeper: %d, incstep: %d, sscgr: 0x%08x\n",
> +                __func__, clk_hw_get_name(hw), modeper, incstep, sscgr);

Do we need to keep all this pr_debug()? It's tested code right?

> +       writel(sscgr, base + STM32F4_RCC_SSCGR);
> +}
> +
>  static int stm32f4_pll_set_rate(struct clk_hw *hw, unsigned long rate,
>                                 unsigned long parent_rate)
>  {
> @@ -683,6 +732,9 @@ static int stm32f4_pll_set_rate(struct clk_hw *hw, unsigned long rate,
>  
>         writel(val, base + pll->offset);
>  
> +       if (pll->ssc_enable)
> +               stm32f4_pll_set_ssc(hw, parent_rate, n);
> +
>         if (pll_state)
>                 stm32f4_pll_enable(hw);
>  
> @@ -788,6 +840,87 @@ static struct clk_hw *clk_register_pll_div(const char *name,
>         return hw;
>  }
>  
> +static int stm32f4_pll_init_ssc(struct clk_hw *hw, struct stm32f4_pll_ssc *conf)

__init

const conf?

> +{
> +       struct clk_gate *gate = to_clk_gate(hw);
> +       struct stm32f4_pll *pll = to_stm32f4_pll(gate);
> +       struct clk_hw *parent;
> +       unsigned long parent_rate;
> +       int pll_state;
> +       unsigned long n, val;
> +
> +       parent = clk_hw_get_parent(hw);
> +       if (!parent) {
> +               pr_err("%s: failed to get clock parent\n", __func__);
> +               return -ENODEV;
> +       }
> +
> +       parent_rate = clk_hw_get_rate(parent);
> +
> +       pll->ssc_enable = true;
> +       memcpy(&pll->ssc_conf, conf, sizeof(pll->ssc_conf));
> +
> +       pll_state = stm32f4_pll_is_enabled(hw);
> +
> +       if (pll_state)
> +               stm32f4_pll_disable(hw);
> +
> +       val = readl(base + pll->offset);
> +       n = FIELD_GET(STM32F4_RCC_PLLCFGR_N_MASK, val);
> +
> +       pr_debug("%s: pll: %s, parent: %s, parent-rate: %lu, n: %lu\n",
> +                __func__, clk_hw_get_name(hw), clk_hw_get_name(parent),
> +                parent_rate, n);
> +
> +       stm32f4_pll_set_ssc(hw, parent_rate, n);
> +
> +       if (pll_state)
> +               stm32f4_pll_enable(hw);
> +
> +       return 0;
> +}
> +
> +static int stm32f4_pll_ssc_parse_dt(struct device_node *np,

__init

> +                                   struct stm32f4_pll_ssc *conf)
> +{
> +       int ret;
> +       const char *s;
> +
> +       if (!conf)
> +               return -EINVAL;
> +
> +       ret = of_property_read_u32(np, "st,ssc-modfreq-hz", &conf->mod_freq);
> +       if (ret)
> +               return ret;
> +
> +       ret = of_property_read_u32(np, "st,ssc-moddepth-permyriad",
> +                                  &conf->mod_depth);
> +       if (ret) {
> +               pr_err("%pOF: missing st,ssc-moddepth-permyriad\n", np);
> +               return ret;
> +       }
> +
> +       ret = of_property_read_string(np, "st,ssc-modmethod", &s);
> +       if (ret) {
> +               pr_err("%pOF: missing st,ssc-modmethod\n", np);
> +               return ret;
> +       }
> +
> +       if (!strcmp(s, "down-spread")) {
> +               conf->mod_type = STM32F4_PLL_SSC_DOWN_SPREAD;
> +       } else if (!strcmp(s, "center-spread")) {
> +               conf->mod_type = STM32F4_PLL_SSC_CENTER_SPREAD;
> +       } else {
> +               pr_err("%pOF: wrong value (%s) for fsl,ssc-modmethod\n", np, s);
> +               return -EINVAL;
> +       }

Can you use match_string() like fwnode_property_match_property_string()
does?

> +
> +       pr_debug("%pOF: SSCG settings: mod_freq: %d, mod_depth: %d mod_method: %s [%d]\n",
> +                np, conf->mod_freq, conf->mod_depth, s, conf->mod_type);
> +
> +       return 0;
> +}
> +
>  static struct clk_hw *stm32f4_rcc_register_pll(const char *pllsrc,
>                 const struct stm32f4_pll_data *data,  spinlock_t *lock)
>  {